The need to artificially introduce food into the gastrointestinal tracts of individuals who can not eat, or will not eat, has been well-known throughout and even prior to this century. Before the mid-1970's, feeding was done nasogastrically with red rubber or polyvinylchloride feeding tubes. The use of enteral feeding by means of nasogastric tubes expanded dramatically in the late 1970's with the introduction of tubes constructed of either silicone rubber or polyurethane. Being constructed of stronger materials, these tubes incorporated thinner walls, and were therefore smaller in outside diameter. These smaller tubes were easier to insert and more comfortable for the patient, and their introduction resulted in a very rapid growth of enteral nutrition via the nasogastric route, and increased interest in enteral nutrition in general.
By the 1980's problems with nasogastric feeding were recognized by clinicians and the advantages of direct gastrostomy access into the stomach through the abdominal wall had been described by Vazquez in U.S. Pat. No. 4,356,824, and by Moss in U.S. Pat. No. 4,543,085. Refinements in securing gastrostomy tubes in the patient were described by Parks in U.S. Pat. No. 4,666,433 and in U.S. Pat. No. 4,685,901.
The 1980's also saw the refinement of methods for forming the gastrostomy stoma. Prior to the 1980's, the stoma or gastrostomy was formed surgically by the Stamm procedure, which required a surgical laporatoratomy to insert the tube, usually a latex urologic Foley retention catheter. A new method, called a "PEG", or Percutaneous Endoscopic Gastrostomy, eliminated the need for a surgical gastrostomy to place the gastrostomy tube and dramatically expanded the interest in the use of direct gastrostomy tubes. The advantages of PEGs and the PEG technique were described by Quinn et al. in U.S. Pat. No. 4,795,430. The word "PEG" is used herein to identify both the tube and the procedure.
Gastrostomy tubes can generally be organized into three main groups, the third of which includes two subgroups:
1. SPECIALTY TUBES placed at the time of gastric surgery by the Stamm technique. The Moss and Vazquez patent tubes are examples of this type.
2. PEG TUBES which are used to form the initial stoma or gastrostomy.
3. REPLACEMENT TUBES which are used to replace PEG TUBES after a period of time because a PEG TUBE has worn out with use, or because a device which is more specific to the patient's need is required. These tubes are inserted into the original stoma created by either the PEG TUBE or the Stamm technique.
a. LOW PROFILE REPLACEMENT TUBES which are preferred for active patients who wish to conceal the tube's outer fitments during periods when they are not receiving feeding formula. The background for this type of replacement tube is described by Quinn et al. in U.S. Pat. No. 5,125,897. PA1 b. SIMPLE REPLACEMENT tubes which are less complicated and less expensive are used for patients who are not active and have no need to hide their device. These devices are direct modifications of the original urologic Foley catheters used in early gastrostomies. They are described by Parks in U.S. Pat. No. 4,666,433.
With some exceptions within individual designs, gastrostomy tubes or tube assemblies of the aforedescribed types each incorporate the following seven features or components:
1. A tube to carry the enteral feeding formula into the stomach and or the intestine.
2. An outflow port in the distal end of the tube. The port or ports may be incorporated in the end or the sidewall of the tube. They may also be incorporated in a separate, molded bolus fastened to the distal end of the tube.
3. An administration set connector attached to the proximal end of the tube, which is outside of the patient.
4. A distal end retention device or internal bolster to hold the tube in the stomach, e.g., an inflatable balloon or a molded retention shape which can be deformed with a stylet for insertion and removal.
5. An external bolster to secure the tube at the point where it exits the skin. This bolster maintains the proper distance between the external bolster and the internal retention device, a distance corresponding to the combined thickness of the individual patient's skin, abdominal wall and stomach wall at the site of the gastrostomy.
6. An anti-reflux valve to prevent leakage of gastric acids from the patient when the administration set is being changed or when violent coughing causes excessive back pressure.
7. A measurement system to measure the patient's abdominal wall thickness so that the tube length between the retention device and the external bolster can be adjusted to match this thickness.
In addition to gastrostomy, tubes or tube assemblies of this type are used to administer drugs to, or drain urine from, the bladder. Such tubes or tube assemblies are referred to as suprapubic catheters and comprise the same seven features or components referred to above in the context of gastronomy tubes or tube assemblies. However, they access the bladder through a stoma formed in the abdominal wall above the bladder or pubic area.
The feature of gastrostomy and other corporeal access tube assemblies with which the present invention is concerned is the distal end retention device. Distal end retention devices take many forms. Some are simply an inflatable balloon which is collapsible to permit removal. Others use non-inflatable, preformed structures which can be physically deformed to permit removal. Others are combinations of these approaches. Shermeta U.S. Pat. No. 3,915,171, Quinn et al. U.S. Pat. No. 4,981,471 and Andersen et al. U.S. Pat. No. 5,439,444 disclose exemplary devices.
Tubes with inflatable silicone retention balloons are easy to insert because the uninflated balloons are formed completely flat against the tube wall. However, they are unreliable because the silicone balloon walls, which are stretched thin when expanded, tend to break easily. Preformed, molded internal retention devices must be deformed with a stylet and are difficult to insert and remove, although they are generally reliable once they are in place.